As evidence grew that high blood cholesterol levels were linked to heart disease, scientists in both academia and industry began to look for drugs to lower cholesterol as early as the 1950s. Before Akira Endo discovered the first statin, mevastatin, in the 1970s, many things, including hormones, vitamins, and resins, were tried to lower cholesterol. Some worked, and some did not. Thyroid hormone was one of the fi st drugs used for that purpose. The cholesterol-lowering properties of dextro-thyroxine were discovered by serendipity. At one point, surgical removal of part of the thyroid gland had been used to relieve angina, the pain brought on by exercise in coronary artery disease. Doctors observed that thyroid removal also raised the blood cholesterol level, which in turn sped up arterial degeneration. By deduction, the doctors reasoned that taking thyroid hormone should then decrease blood cholesterol levels. Initial clinical trials proved this theory, and dextro-thyroxine was used to lower cholesterol beginning in the 1950s, when thyroid extract became a standard treatment for hypercholesterolemic (high cholesterol) patients. Unfortunately, too much thyroid hormone made patients tremble all the time. Later, a large-scale, long-term clinical trial named the “Coronary Drug Project” established the association of dextro-thyroxine with ischemic heart disease as a severe side eff ect in men. As a consequence, thyroid hormone treatment was discontinued. Women, in contrast to men, enjoy natural cardiac protection through the action of the female sex hormones, the estrogens. In 1930, a minute quantity of estrogen was isolated from the ovaries of 80,000 sows. In the 1950s, reports appeared that estrogen could lower blood cholesterol levels even more effectively than nicotinic acid, another anticholesterol drug used at the time. Unfortunately, men on estrogen for too long began to develop feminine traits, including breast enlargement and loss of libido, and other side effects, although they did acquire relative immunity from heart attacks until late in life. Due to the lack of safe and effiicacious drugs, some doctors seemed willing to take their chances with estrogens.
Thyroid hormone treatment and SARS-CoV-2 infection
